Astbury Center for Structural Molecular Biology, School of Molecular and Cellular Biology, University of Leeds, Leeds, LS2 9JT, UK.
Department of Biology, University of York, York, YO10 5DD, UK.
J Am Soc Mass Spectrom. 2017 Sep;28(9):1855-1862. doi: 10.1007/s13361-017-1689-9. Epub 2017 May 8.
Collision cross-section (CCS) measurements obtained from ion mobility spectrometry-mass spectrometry (IMS-MS) analyses often provide useful information concerning a protein's size and shape and can be complemented by modeling procedures. However, there have been some concerns about the extent to which certain proteins maintain a native-like conformation during the gas-phase analysis, especially proteins with dynamic or extended regions. Here we have measured the CCSs of a range of biomolecules including non-globular proteins and RNAs of different sequence, size, and stability. Using traveling wave IMS-MS, we show that for the proteins studied, the measured CCS deviates significantly from predicted CCS values based upon currently available structures. The results presented indicate that these proteins collapse to different extents varying on their elongated structures upon transition into the gas-phase. Comparing two RNAs of similar mass but different solution structures, we show that these biomolecules may also be susceptible to gas-phase compaction. Together, the results suggest that caution is needed when predicting structural models based on CCS data for RNAs as well as proteins with non-globular folds. Graphical Abstract ᅟ.
碰撞截面（CCS）测量值可从离子淌度质谱联用仪（IMS-MS）分析中获得，这些测量值通常可以提供有关蛋白质大小和形状的有用信息，并且可以通过建模程序进行补充。然而，人们对某些蛋白质在气相分析过程中保持天然构象的程度存在一些担忧，尤其是具有动态或扩展区域的蛋白质。在这里，我们测量了一系列生物分子的 CCS，包括非球形蛋白质和不同序列、大小和稳定性的 RNA。使用行波 IMS-MS，我们表明，对于所研究的蛋白质，测量的 CCS 与基于当前可用结构的预测 CCS 值有很大差异。所呈现的结果表明，这些蛋白质在进入气相时会根据其延伸结构的不同而发生不同程度的折叠。比较两个质量相似但溶液结构不同的 RNA，我们表明这些生物分子也可能容易在气相中发生紧缩。总之，这些结果表明，在基于 CCS 数据预测 RNA 以及具有非球形折叠的蛋白质的结构模型时需要谨慎。
